/interpreter/tags/at2dist220411/src/edu/vub/at/objects/natives/grammar/AGSelf.java

 1/**
 2 * AmbientTalk/2 Project
 3 * AGSelf.java created on 27-jul-2006 at 12:57:41
 4 * (c) Programming Technology Lab, 2006 - 2007
 5 * Authors: Tom Van Cutsem & Stijn Mostinckx
 6 * 
 7 * Permission is hereby granted, free of charge, to any person
 8 * obtaining a copy of this software and associated documentation
 9 * files (the "Software"), to deal in the Software without
10 * restriction, including without limitation the rights to use,
11 * copy, modify, merge, publish, distribute, sublicense, and/or
12 * sell copies of the Software, and to permit persons to whom the
13 * Software is furnished to do so, subject to the following
14 * conditions:
15 *
16 * The above copyright notice and this permission notice shall be
17 * included in all copies or substantial portions of the Software.
18 *
19 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
20 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
21 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
22 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
23 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
24 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
25 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
26 * OTHER DEALINGS IN THE SOFTWARE.
27 */
28package edu.vub.at.objects.natives.grammar;
29
30import edu.vub.at.exceptions.InterpreterException;
31import edu.vub.at.objects.ATContext;
32import edu.vub.at.objects.ATObject;
33
34import java.util.HashSet;
35import java.util.Set;
36
37/**
38 * @author tvc
39 *
40 * The abstract grammar element denoting the symbol 'self'
41 */
42public final class AGSelf extends AGSymbol {
43
44	private static final String SELF_NAM = "self";
45	
46	public static final AGSelf _INSTANCE_ = new AGSelf();
47	
48	private AGSelf() { super(SELF_NAM); }
49	
50	/**
51	 * To evaluate a self reference, simply select the current self from the current evaluation context.
52	 * 
53	 * AGSelf().eval(ctx) = ctx.self
54	 */
55	public ATObject meta_eval(ATContext ctx) throws InterpreterException {
56		return ctx.base_receiver();
57	}
58
59	/**
60	 * Quoting a self reference results in the same self reference.
61	 */
62	public ATObject meta_quote(ATContext ctx) {
63		return this;
64	}
65	
66	/**
67	 * After deserialization, ensure that the self pseudovariable remains unique.
68	 */
69	public ATObject meta_resolve() throws InterpreterException {
70		return _INSTANCE_;
71	}
72	
73	/**
74	 * FV(self) = { }
75	 */
76	public Set impl_freeVariables() throws InterpreterException {
77        return new HashSet();
78	}
79	
80}